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Posted by Sherman in Idaho [24.32.202.166] on Wednesday, January 02, 2013 at 14:32:11 :
In Reply to: Casing gas, wood gas, marijuana....Alternative energy posted by Caleb (Manhattan, KS) [70.184.232.53] on Wednesday, January 02, 2013 at 14:05:25 :
I've been interested in "gassification" technology ever since my dad told me about bombing the "synthetic oil plants" during the war. Later I wondered just what it was he was bombing, and got to reading about the Fischer-Tropsche process for converting coal into methane and then into fuel oil. It's not so good for making gasoline, though, which is why the Germans pushed so hard on turbine engines during the war. The basic process is to heat coal red-hot and then blow steam into it, just like in an old-fashioned city gas plant. The Fischer-Tropsche part of the process uses pressure and a catalyst (iron or nickel) to convert the resulting hydrogen and methane into larger hydrocarbons that can be condensed as a liquid fuel.
The gassifiers for vehicle power are simpler and cruder, but they have the great advantage of operating at atmospheric pressure. They produce a mixture of hydrogen, methane, methanol, turpentine, tar, and everything in between. The better vehicle gassifiers at least attempt to keep the tar and the ash from going into the engine.
A stationary "home made" plant like you suggest would of course be better if you could produce a portable liquid or compressed gas fuel from it, but in order to save the hydrogen and methane, which can't be compressed into a liquid like propane and reasonable pressures, you need to combine those small molecules into larger hydrocarbon molecules by adding carbon (easy enough) at high pressure and temperature (not so easy).
To do it right, you're basically building an old-fashioned city gas plant combined with an oil refinery, on a small scale in your back yard. Getting the chemistry right quickly goes beyond what a guy can cobble together from scrap metal and a torch. You'll be dealing with combustible materials -- solids, liquids, and gasses -- at temperatures up to 1000 degrees and pressures up to 150 psi. Even modern oil refineries blow up from time to time.
I really wish more people would try building such systems on a back yard scale, but realistically you need deep pockets, a really good shop, and a big piece of land. If your gas generator / oil refinery / bomb is within sight, sound, or smell of any neighbors, the zoning and environmental authorities are likely to take a dim view of it. The technology itself is 80 years old, but that doesn't mean it's simple.